Patients undergoing abdominal or thoracic surgery remain hospitalized during recovery following such procedures. Even after patients are mobile and the risks of infection are minimal, patients are not discharged until they have demonstrated normal bowel function, most often via passage of gas and/or a bowel movement. Depending on the specific surgery, the typical length of stay (LOS) in the hospital is three or four days post-surgery. There is also a risk that the patient will not demonstrate normal bowel function in the typical timeframe and will need to remain in the hospital for several additional days or more. The likelihood of such an outcome varies by type of surgery and ranges from a few percent to upwards of twenty percent. When this situation arises, the patient is said to have developed post-operative ileus (POI).
Owing to the resulting distress to the patient of an extended LOS, risks of secondary infection, and cost to the healthcare system, it is an aim of most healthcare systems to avoid such cases of POI. It is a further aim to accelerate the discharge of patients not developing POI in order to minimize the hospital stay while also ensuring patient readiness for discharge and minimizing the likelihood of hospital readmission.
Motor activity, the muscular action of the smooth muscles in the walls of the stomach, small intestine, and colon under control of the enteric nervous system, mixes and propels the contents of these organs (i.e., chyme). This action supports digestion and drives motility, the normal movement of the thyme through the body, including eventual defecation. Immediately following abdominal and similar surgery, motor activity halts, gradually recovering over the next few days, organ by organ. Current literature estimates that during the post-operative period, the motor activity of the small intestine recovers within 8 to 24 hours, of the stomach at about 24 hours, and of the colon between 36 to 48 hours, while noting that these estimates contain considerable uncertainty due to a lack of direct measurements.
Unfortunately, at present, no reliable means of assessing the recovery of the GI tract exist short of the endpoint determination of flatus and bowel movement. Hospital staff and physicians monitor a patient's willingness to consume liquids and liquid meals, check for signs of nausea afterward, and periodically listen for abdominal sounds with a stethoscope during the first days after surgery. Yet none of these are reliable signs of incipient recovery of normal GI tract function. All have known weaknesses delineated in the literature.
U.S. Pat. No. 5,301,679 by Taylor teaches a means of measuring bowel sounds and relating the recordings to bowel activity, with an aim of addressing the same issue discussed here. This represents an automated version of the stethoscope technique, and underscores the need for a means of determining motor activity of the GI tract during surgical recovery. The approach suffers from the same fundamental limitation of the stethoscope in that the relationship of sounds recorded at the abdominal surface to motor activity is not well established. In fact, this approach is viewed by many as an unreliable indicator of motor activity.
Accordingly, there is a need for systems and methods that are able to directly measure the motor activity of the stomach, small intestine, and colon as they recover function, to monitor the recovery of said organs after surgery. With this information, hospital staff would be able to determine which patients are progressing slowly and which are moving along quickly and adjust treatment accordingly. With this information, extended hospital LOS due to ileus may be minimized and optimal treatment of non-ileus patients may allow accelerated discharge. Further, with a definitive signal of motor activity in each major GI organ, the confidence staff has in recommending discharge may be greater than currently obtained by monitoring flatus and bowel movements. As a result, the incidence of hospital readmission may decrease.